Device to obtain a glazing surrounded by cast plastic

ABSTRACT

A device for obtaining a glazing surrounded, on at least a portion of its periphery, by cast plastic including an injection head, a cavity, an injection dam and at least one mold part in the wall of which a duct is provided. The duct has two parts, one part located outside the joint plane and one part located in the joint plane.

This is a Division of application Ser. No. 08/261,972 filed on Jun. 17,1994.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a device for obtaining a glazing surrounded, onat least a portion of its periphery, by cast plastic. The invention alsorelates to the method and device for obtaining such a glazing.

2. Description of the Related Art

The plastic surrounding the glazing on at least a portion of itsperiphery can constitute a seal and/or an assembly joint therefor.Functional elements such as fastening means, guiding means, etc. canalso be present either in the form of inserts, e.g., at least partiallyburied in the plastic, or formed from this plastic. Usually thisplastic, or encapsulation material, covers at least the width of theedge of the glazing.

Regardless of the function of the encapsulation material, the castglazing is generally obtained by injecting the plastic into a mold inwhich the glazing is previously placed. This mold itself consists of twoparts, a lower part and an upper part, also called a mold andcountermold. After having closed the mold, the plastic is injected intoa mold cavity by an injection head. A feed duct is provided in the wallof the mold to route the plastic from the injection head to the cavityof the mold. This duct can have any shape. The end of the injectionduct, constituting a boundary between the feed duct and the cavity ofthe mold, is usually called an injection dam. It constitutes a type ofentry for the plastic into the cavity.

Usually, the injection head and the feed duct are located at the levelof the joint plane defined by the surface located between the two partsof the mold, i.e., the surface of one of the parts of the mold, forexample the upper part, intended to come in contact with the surface ofits complementary part, for example the lower part.

This arrangement has the advantages of simplifying the design of themold and of locating the injection dam at the level of the edge of theglazing, advantageously at the center of the edge of the glazing.

However, the plastic formed in the feed duct constitutes an excess partthat must be eliminated after removal from the mold. When the injectiondam is relatively thick, particularly for glazings of large dimensions,this operation is difficult. It often causes defects such as a reductionof the thickness of the encapsulation material, that can be seen.Furthermore, when the encapsulation material forms a lip of smallthickness at the level of the injection dam, the elimination of theexcess plastic is difficult and sometimes damages the lip.

Furthermore, during the injection of the plastic it is necessary todrive out the air present in the cavity to prevent any formation ofbubbles and/or a poor filling of the cavity. Vents can be provided forthis purpose. However, in certain cases, they are not entirelysatisfactory.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a device whose design issimple and that makes possible an easy elimination of the excessplastic.

It is a further object of the invention to provide a glazing surrounded,on at least a portion of its periphery, by cast plastic. The deviceincludes an injection head, a cavity, an injection dam and at least onemold part in the wall of which a duct is provided and houses saidinjection dam. The duct has two parts, one part located outside thejoint plane and one part located in the joint plane.

The injection dam is thus located, according to the invention, on a faceof the encapsulation material covering at least a portion of theglazing, advantageously on the face of the encapsulation materialintended to be hidden: the removal of the excess plastic does not thenrun the risk of damaging the encapsulation material and particularly itslip. Furthermore, the device of the invention offers an additionaladvantage of easy removal of the excess plastic formed in the duct.

According to an embodiment of the invention, the injection head islocated in the joint plane, particularly in the extension of the part ofthe duct located in this plane. The design of the mold as well as theremoval of the excess plastic from the duct are thereby accordinglyfacilitated.

The device of the invention includes at least one mold consisting of twoparts.

A duct is provided in the wall of one of the parts of the mold. A partof this duct is located, according to the invention, outside the jointplane. It has, at one of its ends, the injection dam.

This part can be curved or a flat panel. Preferably, it comprisesseveral segments, these segments being curves and/or panels. Thesesegments can have a parallelepiped or cylindrical shape.

The radii of curvature or the angles of the panels with respect to thejoint plane depend on the shape and dimensions of the encapsulationmaterial. When it is an inclined panel, the angle is, for example,between 30° and 60° in relation to the joint plane.

This part of the duct according to the invention is advantageouslycomposed of at least two segments. Preferably, the end of the firstsegment in contact with the second segment, or entry appendage,constitutes a break line. The plastic formed in the second segment,whose end constitutes the injection dam, or entry appendage, ispreferably separated from the rest of the plastic formed in the firstsegment, during the opening of the mold. To constitute a break linebetween the entry appendage and at least one segment, the end of thesegment in contact with the entry appendage exhibits a small thickness.This thickness is a function of the geometry of the break line as wellas of the tearing strength of the material used. Advantageously, theentry appendage is perpendicular to the joint plane. After opening ofthe mold, the excess plastic remaining in the feed duct is thus easilywithdrawn. The plastic formed in the entry appendage is integral withthe encapsulation material and is removed by sectioning, for example byuse of a cutting blade followed, optionally, by brushing.

As for the part of the mold located in the joint plane, it has anyshape, preferably approximately straight to limit its length.

The volume of the duct of the invention is advantageously limited, onthe one hand, to simplify the design of the mold and, on the other hand,to reduce the amount of excess plastic. This volume is a function of thedimensions of the glazing to be encapsulated. It is on the order of 10to 15% of the volume of the cavity of the mold. To do this, the part ofthe duct located in the joint plane preferably consists of two segments,preferably two panels: a first segment inclined in relation to the jointplane and a second segment, or entry appendage, one end of whichconstitutes the injection dam. It connects the first inclined segment tothe cavity of the mold. According to an advantageous variant, the devicecomprises only one injection dam.

The invention also relates to a method for obtaining a glazingsurrounded, on at least a portion of its periphery, by cast plasticusing a device of the invention. The method comprises, in particular,the following steps:

positioning of the glazing in one of the parts of the mold and,optionally, of inserts,

closing of the complementary part of the mold,

injection of the plastic,

opening of the mold,

removal of the excess plastic formed in the duct and at the level of theencapsulation material.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a section, in perspective, of a conventional glazing;

FIG. 2 is a section, in perspective, of a glazing according to theinvention;

FIG. 3 is a longitudinal section of a mold according to the invention;

FIGS. 4a and 4b comprise two diagrams schematically representing alongitudinal section of two variants of feed ducts according to theinvention, and

FIG. 5 shows the glazing according to the invention after opening of themold.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, wherein like reference numerals designateidentical or corresponding parts throughout the several views, and moreparticularly to FIG. 1 thereof, in FIG. 1, glazing 1 is surrounded by aconventional plastic 2 covering edge 3 of the glazing. The plastic, orencapsulation material, 2 comprises a lip 4 of small thickness intendedto cover the bodywork opening or any other support. The plastic is shownas overflowing on faces 5 and 6 of the glazing. It can also be flushwith one of the two faces 5 or 6, or with both faces 5 and 6. Theinjection dam, referenced at 7, and optionally not visible, is locatedin the center of the edge of the glazing. The visible face, once theglazing is mounted in the bodywork opening, is face 6.

FIG. 2 shows a glazing according to the invention. Injection dam 8 islocated on face 9 of the encapsulation material overflowing on face 5 ofthe glazing. It is the hidden face when the glazing is mounted in thebodywork opening. It can also be located on the face of theencapsulation material overflowing on face 6 of the glazing.

FIG. 3 shows a portion of the device according to the invention. Thedevice comprises, in particular, a mold. The mold consists of two parts,an upper part 10 and a lower part 11, forming cavity 12 of the mold.This cavity is shown here in the upper part and the lower part of themold. It can also be located only in the upper or lower part.

The duct according to the invention comprises two parts 13 and 17. Part13 is located outside the joint plane, represented as A. In this Figure,it comprises two segments 14 and 16: a first inclined panel 14 and, incontact with its end 15, a second panel or entry appendage 16. The endof the entry appendage constitutes injection dam 8.

Inclined panel 14 forms an angle α with joint plane A. This angle is,advantageously, between 30° and 60°.

The width of inclined panel 14 can decrease in the direction of thethickness of the mold, as illustrated in the Figure. It can alsoincrease or be constant. Of course, the dimensions of inclined panel 14are independent of those of the duct. Also, the dimensions of panel 16can vary as a function of the dimensions of end 15 of inclined panel 14and as a function of the dimensions of injection dam 8. Thesedimensions, more specifically the thickness multiplied by the width, areapproximately proportional to the amount of material necessary to formthe encapsulation material.

To form a break line between entry appendage 16 and inclined panel 14,the thickness of end 15 of panel 14 is, for example, less than or equalto 4 mm and, preferably, less than or equal to 2 mm. Preferably, thethickness of inclined panel 14 decreases in the direction of thethickness of the mold (e.g., toward the left in FIG. 3) to form a sortof bevel, not shown, at its end 15. Thus, a satisfactory break line isobtained at end 15 while maintaining a certain amount of material formedin inclined panel 14 to facilitate its removal after opening of themold. For the same reason, entry appendage 16 is, preferably,perpendicular to joint plane A.

Duct part 17 of the invention is located in joint plane A. It can be inthe extension of injection head 18. The latter is, for example, aninjection nozzle. It is located, preferably, in the extension of jointplane A.

This part 17 can have any shape. It can be, for example, a duct with acylindrical or parallelepiped or trapezoidal shape. It can also havecurves.

When the injected material is of the RIM (Reaction Injection Molding)type, it preferably includes a static mixer or static mixers near theinjection head.

The length of part 17 is a function of the envisaged use. It can berestricted to a few centimeters.

The dimensions of the duct of the invention are such that the plasticformed in the duct can easily be removed from the mold, while assuring ahomogeneous flow to feed the cavity of the mold. Movable parts of themold can also be provided to facilitate the removal from the mold.

FIGS. 4a and 4b show two variants of the duct according to theinvention. The part of duct 13 comprises, in these variants, twosegments 19 and 20. Segment 19 can be curved, as illustrated in FIGS. 4aand 4b. Also, segment 20, or entry appendage, can be inclined withrespect to the joint plane, as illustrated in FIG. 4b. It isadvantageously perpendicular to the joint plane, as illustrated in FIG.4a. The angles defined respectively by segment 19 and by segment 20 withrespect to the joint plane are advantageously such that the plasticformed in these two segments can easily be removed from the mold.Furthermore, movable elements can be provided to remove the excessplastic from the mold.

Of course, any variant can be envisaged without departing from thespirit of the invention.

FIG. 5 illustrates the cast or encapsulated glazing after the opening ofthe mold. Plastic 21 formed in entry appendage 16 is then integral withencapsulation material 2. It can be removed by a cutting blade followed,optionally, by a brushing. Any other suitable means can also beenvisaged.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed as new and is desired to be secured by Letters Patent ofthe United States is:
 1. Device for obtaining a glazing surrounded, onat least a portion of its periphery, by a cast plastic, comprising:amold comprising two parts separated by a joint plane and defining acavity, and a duct comprising an injection dam connected to said cavityfor injecting a plastic material into said cavity to form the castplastic, said injection dam being connected to said cavity at a portionof said cavity corresponding to a face of the cast plastic covering atleast a portion of the glazing, wherein said duct comprises two parts,one part outside the joint plane and ending in said injection dam, andanother part in the joint plane and connected to said one part; and aninjection head located in the joint plane for supplying the injectionmaterial to the part of the duct in the joint plane.
 2. Device accordingto claim 1, wherein said injection head is located in the joint plane.3. Device according to claim 1, wherein the one part of said ductcomprises two segments, a first segment inclined in relation to thejoint plane and a second segment having one end comprising saidinjection dam.
 4. Device according to claim 3, wherein the first segmenthas an end in contact with the second segment to define a break line. 5.Device according to claim 1, wherein the one part of said duct comprisestwo flat panels, a first panel inclined in relation to the joint planeand a second panel having an end comprising the injection dam.
 6. Deviceaccording to claim 1, wherein a volume of the duct is between 10 and 15%of the volume of the cavity.
 7. Device according to claim 1, whereinsaid injection head comprises means for injecting a Reaction InjectionMolding plastic.
 8. Device according to claim 4, wherein a thickness ofsaid duct is reduced at said break line as compared to a remainder ofsaid duct.